Question

Which of the following is/are possible reason(s) for linkage disequilibrium between alleles at two loci?

• A. Low recombination rate between loci
• B. High recombination rate between loci
• C. Natural selection
• D. Polyploidy

Hint:

Low recombination and selection maintain non-random allele associations.

Answer 1

The Correct Option is A, C

To understand why linkage disequilibrium (LD) may occur between alleles at two loci, we need to explore the mechanisms responsible for this genetic phenomenon. Linkage disequilibrium refers to the non-random association of alleles at two or more loci. The correct options for potential reasons for linkage disequilibrium between alleles at two loci are:

1. Low recombination rate between loci
2. Natural selection

Explanation:

• Low Recombination Rate Between Loci:
  • Recombination is the process where genetic material is exchanged between homologous chromosomes during meiosis. A low recombination rate means that alleles located close together on the same chromosome are less likely to be separated during this process.
  • Consequently, alleles that are physically close on a chromosome are inherited together more often than those further apart, leading to linkage disequilibrium between those loci.
• Natural Selection:
  • Natural selection can promote linkage disequilibrium when a combination of alleles at different loci increases an organism's fitness.
  • If a specific haplotype confers a survival or reproductive advantage, those alleles will be inherited together more frequently, maintaining linkage disequilibrium despite potential recombination.
• High Recombination Rate Between Loci (Incorrect):
  • A high recombination rate would reduce linkage disequilibrium as alleles at different loci are more likely to be shuffled and inherited independently.
• Polyploidy (Incorrect):
  • Polyploidy refers to the condition of having more than two complete sets of chromosomes. While polyploidy can influence genetic variation and evolution, it doesn't directly cause linkage disequilibrium between alleles at two loci.

Conclusion:

The most valid reasons for linkage disequilibrium between alleles at two loci are low recombination rates, which cause alleles to be inherited together, and natural selection, which favors specific allele combinations. The correct options are "Low recombination rate between loci" and "Natural selection."